Two piece arc plate assembly



Marh 30, 1965 A. E. STRINGFELLOW 3,176,102

TWO PIECE ARC PLATE ASSEMBLY Filed March l0. 1961 4H .,r/ l E y irme/vds United States Patent O 3,176,102 TWO PIECE ARC PLATE ASSEMBLY vAllen E. Stringfellow, Haddoniield, NJ., assignor t I-T-E Circuit` Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 10, 1961, Ser. No. 94,762 11 Claims. (Cl. Zim- 144) My invention relates to circuit breakers, and more particularly to circuit breaker arc chutes having a novel two-piece arc plate construction.

Circuit 'breakers presently in use are designed to include arc chutes to aid in the rapid extinguishment of an arc ywhich is formed during the tripping operation. Sin'ce circuit breakers are tripped to interrupt current of relatively high magnitude, the arc current `created as a result of the tripping operation has the same magnitude as the fault current.

The high magnitude arc current created during the tripping operation causes the gases present in the arc chute to be rapidly heated and ionized. The rapidly expanding gases place severe stress on the arc chute and on its associated elements, mainly ythe arc plates. This explosion which accompanies the tripping operation is the most significant factor to be considered in the design of the arc chute and its arc plates.

The are chutes of the prior art contain a plurality of spaced parallel arc plates which are interposed between a pair of arc runners contained in thearc chute. The arc plates are formed of insulating or non-conductive material. The :arc plates create a tortuous path for the electric arc as it travels upward along the arc runners. rlhe lower portion of each arc plate contains an elongated slot which tapers inward to for-m an inverted V-shaped notch. The region bounded by the slots permit the hot ionized gases to rise rapidly .above the separating `contacts and the lower portions of the arc runners thereby preventing a restrike or ilashover between the `contacts and between the lower portions (arc horns) of the arc runners. Since the region bounded by the inverted V-shaped slots is the path of least resistance in the arc chute, 4the arc will confine itself to this region when it is first transferred to the arc runners.

In order to create a more tortuous path for the arc when the arc is contained in the region bounded by the are plate slots, the arc plates have been designed so that the vertex of the V-shaped slot lies to the right of the arc plate longitudinal axis. The arc plates are then stacked in the arc chute in a staggered fashion so that the vertices of alternate arc plates lie to the right of the arc plate longitudinal axis and the vertices of the remaining arc plate slots lie to the left of the arc plate longitudinal axis. This staggered design causes the upward moving arc to be elongated in the horizontal plane as it travels through the region bounded by ythe arc plate slots.

Since the rapid extinguishment of the arc is of the utmost importance, it is desirable to elongate the arc as much as possible when it lies in the region of the arc plate slots. One manner of doing this is to taper the lower portion of the arc plate and alternate the tapered edges of adjacent arc plates in the arc chute. This design will give the greatest possible horizontal elongation of the arc when the arc is in the region bounded by the tapered edges. The stacking of arc plates having this configuration however, must be done in such a manner as to prevent any sidewise movement of the arc plates due to the explosion which takes place during the tripping operation. One method of securing the arc plates in the are chute is to form a plurality of slots along the innerfaces ofthe arc chute into which the arc plates may be Aice inserted. Another method is to form anges along the lengthwise edges of the arc plates which serve to space the arc plates from one another. These methods, however, increase the time and complexity of the manufacturing operations. In addition, spacing means of this type are non-resilient, and, therefore, do not allow for Warpage and camber of the arc plates resulting in both a high reject rate of the arc plates and an increase in arc plate breakage.

To overcome these disadvantages, the` prior art has employed resilient spacing means between adjacent arc plates which allow for warpage and camber, and also acts as a shock-absorbent material during the explosion resulting from the tripping operation. The resilient material absorbs the arc-forming shock forces, and thereby diverts these forces from the arc plates, thus preventing the plates from being cracked or broken. The resilient spacing means also forms an excellent seal between adjacent arc plates to prevent ionized gases from leaking out past the sides of the arc plates and shorting out parts of the arc chute which would result in failure of the chute.

One type of resilient means presently in use is a resilient material in rope or cord form which is placed on opposite sides of alternate arc plates immediately adjacent the arc plate edges. The arc plates not having the resilient rope along their edges are interspersed between those arc plates having the resilient rope along their edges. By utilizing the resilient rope in this manner, the rope need only be applied to approximately onehalf of the arc plates for each arc chute.

The parallel arc plate stack is then partially cornpressed and placed in an arc chute shell. Designing arc chutes in this manner results in a decrease in the time and complexity of fabrication.

This simplified spacing means, however, may not be employed with arc plates having tapered edges, but is limited to arc plates having inverted V-shaped slots, since arc plates having tapered edges cannot be properly supported by the resilient rope means.

The arc plate design of my invention consists of a twopiece arc plate. One of the two pieces is similar in design to arc plates having a tapered edge in the lower portion of the arc plate. The other member is designed so that its height is slightly less than the upper end of the taper. A resilient material in rope form is placed on opposite faces of approximately one-half of the arc plates immediately adjacent each edge. The two-piece arc plates which are not bound by the resilient rope are interspersed between the arc plates bound by the resilient rope in a staggered fashion so that the tapered edges of adjacent arc plates are now arranged in alternate fashion. The subassembly is then coated on both sides with an epoxy cement and then cured to form a rigid unitary subassembly. The top and bottom of the subassembly may then be t trimmed to the proper height and also to create a uniform, even surface across the top and bottom. The shorter pieces of each two-piece arc plate act as spacers for the arc plates on either side of it, thereby providing adequate strength to prevent unnecessary sidewise movement and subsequent breakage which may result from the explosion accompanying the tripping operation. It can, therefore, be seen that this design permits the use of arc plates which create the greatest possible horizontal elongation of the arc in combination with resilient rope spacing means.

It is, therefor, one object of my invention to provide a novel arc plate configuration utilizing resilient spacing means.

Another object of my invention is to provide a novel two-piece arc plate.

enr/area Another object of my invention is to provide a novel stacked arc plate coniguration having resilient spacing means.

These and other objects of my invention will become apparent after reading the following description in connection with the drawings, in which:

FIGURE 1 is a side plan View of my novel two-piece arc plate.

FIGURE 2 is an end View of the are plate shown in FIGURE 1.

FIGURE 2a is an end view of the arc plate of FIG- URE 1 showing the manner in which the top and bottom edges of the arc plate are trimmed.

v FIGURES 3 and 3a show two different manners in which the novel two-piece arc plates may be stacked.

FIGURE 4 is a perspective view showing a stacked assembly of arc plates ,of the type shown in FIGURES 1 and 2.

FIGURE 5 is a view of the arc plate assembly of FIG- URE 4 taken along phantom line A-A1 of FIGURE 4.

FIGURES 6 and 6a are side and end views respectively of prior art are plates.

Referring now to the drawings, FIGURE 1 shows the novel arc plate of my invention which is comprised of interrupting member 11 and spacing member 12. The lower portion of interrupting member 11 has a tapered lower edge 13. Spacing member 12 has a tapered edge l14- which cooperates with tapered edge 13 of interrupting member 11 to form a slot 16. The upper end 17 of slot 16 lies to the left of the longitudinal axis shown by phantom line 1S. The height of spacer member 12 is slightly less than the height of tapered edge 13 of interrupter member 11, forming a gap 13. Interrupter member 11 and spacer member 12 may be formed from the same sheet of insulating material for the cost of the are plate alone, enabling the two-piece arc plate to be manufactured at no greater expense than slotted one-piece arc plates ot the prior art. Resilient inorganic cord 19 is secured to the opposite edges of two-piece arc plate 10 in any suitable manner (see FIGURE 2).

One method of arc plate stacking is shown in FIGURE 3. It can be seen that resilient cord 19 need only be secured to alternate arc plates 11a, the remaining are plates 11b being interspersed between the arc plates 11a having the resilient cord 19 secured thereto. It should be noted that the slots 16 (see FIGURE 1) in arc plates 11a have their Vvertices 17 to the left of center line 25, while the slots 16 in arc plates 11b have their vertices lying to the right of center line 25 for a reason to be more fully described. Y

Another manner of applying resilient cord 19 to arc plates 10 is shown in FIGURE 3a. In this embodiment, resilient cord 19 is secured to only one edge of each arc plate 11a and 11b. The arc plates 11a and 11b. are then stacked so that adjacent plates have resilient cord 19 secured to opposite edges. The slots 16 of arc plates 11 are arranged in the same manner as set forth in the description of FIGURE 3.

Y When the desired number of arc plates have been properly stacked, as shown in FIGURE 4, the sidesr`26 of the arc plate assembly are coated withY an epoxy cement to form a rigid unitary assembly. The upper 27 and lower 28 edges are then trimmed, making each suchV assembly of `uniform height and also giving a uniform, even surface across the top and bottom of the assembly. This is done by removing the upper 19a and lower 1% loops of resilient cord Y19 (see FIGURE 2a). Assembly of the arc plates 10 in this manner permits the unitary stacked arc plate assembly to be inserted into the arc chute shell in a relatively simple manner. Y Y

The importance of spacer member 12 shown-in FIG- URE 1 can be seen from consideration of the arc plate configuration shownin FIGURES 6 and 6a. The arc plates 3@ and 31 have tapered edges Stia and 31a respecl. tively, this design being well known in the prior art. Resilient cords Z9 and 29a are secured to the opposite sides of arc plate 30 immediately adjacent each edge. Due to the taper 39a of arc plate 30 resilient cord 29a extends downl only as far as the beginning 3.2 of taper 30a.

As can be seen in FIGURE 6a, are plates 31 which are positioned on opposite sides of are plate 30 are not properly supported and spaced by resilient cord 29a for the portion 32 of their entire height. Y This lack of proper support and spacing results in the breakage of portions 32 of arc plates 31 due to the severe impact which they are exposed to by the explosion accompanying the tripping operation of the associated circuit breaker (not shown). It can thus be seen that arc plates having the contiguration shown in FIGURES 6 and 6a may not successtully be employed in the assembly shown in FIGURE 4. By utilizing spacer member 12, however, the necessary-support is successfully obtained.

The operation of the arc chute is as follows: When the cooperating contacts (not shown) are separated in response .to a fault current condition, an are is drawn between the contacts. The are is urged upward by either magnetic or pneumatic means, causing the arc drawn between the cooperating contacts to transfer to the arc ruuners 20 (see FIGURE 5) located at opposite Vends of the arc chute. At this instant, the arc is in position B as shown in FIGURE 1. The arc is urged upward through the are plates 10 which cause the arc to assume a horizontal zigzag path due to the alternate arrangement of the arc plate slots 16. The arc remains in the region of the slots 16, since the area bounded by the slots offers the least resistance tothe arc. As the are moves still further through the arc chute, it assumes the position of gap 18. FIGURE 5 shows the conguration of the arc B at this instant. It can be seen that the arc B assumes a zigzag configuration due to slots 16 in the two-piece arc plates 1t).V Since the gaps 18 are located at the extreme edges of the arc plate a.,- sembly, this contiguration affords the greatest possible horizontal elongation of the arc when the arc reaches the level of gap 1S. Y

It can, therefore, be seen that I have provided an are plate assembly having a novel two-piece arc plate'which retains all of the advantages of the one-piece arc plates of the prior art, as shown in FIGURE 6, while the two-piece are plate configuration permits the use of resilient cord spacer means which have advantageous shock absorbing qualities.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein, but only by the appending claims.

I claim: 'v

l. An arc plate assembly for a circuit breaker comprising a plurality of two-piece are plates, the members comprising each of said two-piece arc'plates being coplanar,

resilient cord means secured to said arc plates for positioning and securing said arc plates in a spaced parallel arrangement; each of said two piece arc plates being adapted to form a notch therebetween for guiding and elongating an electric current arc to facilitate extinguishment thereof, said resilient cord means being adapted to act as a shock absorber to reduce the impact imparted to the are plate assembly due to a circuit breaker tripping operation, said resilient cord being formed of an inorganic non-conductive material. n

2. An are plate assembly for a circuit breaker comprising a plurality of two-piece arc plates, the members comprising each of said two-piece arc plates being coplanar, resilient cord means secured to said arc plates for positioning and securing said arc plates in a spaced parallel arrangement, said resilient cord means being adapted to act as a shock absorber to reduce the impact imparted to the arc plate assembly due to a circuit breaker tripping operation, said arc plate assembly being treated with an epoxy cement to form a rigid unitary assembly.

3. An arc plate assembly comprising a plurality of two-piece arc plates, the members comprising each of said two-piece arc plates being coplanar, resilient cord means secured to approximately one-half of said arc plates for positioning and securing said arc plates in a spaced parallel arrangement, said resilient cord means having a shock absorbing characteristic to absorb the impact imparted to said arc plates due to a circuit breaker tripping operation; each of said two piece arc plates being adapted to form a notch therebetween for guiding and elongating an electric current arc to facilitate extinguishment thereof.

4. An arc plate assembly comprising a plurality of twopiece arc plates, the members comprising each of said twopiece arc plates being coplanar, resilient cord means for positioning and securing said arc plates in a spaced parallel arrangement, said resilient cord means being secured to the opposite faces of alternate arc plates immediately adjacent -the edges to provide proper spacing for all of said arc plates, an epoxy cement for bonding said assembly, said cement being applied to opposite sides of said assembly to provide a rigid unitary structure.

5. An arc plate assembly comprising a plurality of twopiece arc plates, the members comprising each of said two-piece arc plates being coplanar, resilient cord means for positioning and vsecuring said arc plates in a spaced parallel arrangement, said `cord means being secured to alternate arc plates adjacent one edge of said alternate arc plates and being secured to the remaining arc plates adjacent the edge opposite the said one edge to provide proper spacing for all of said arc plates; each of said two piece are plates being adapted to form a notch therebetween lor guiding and elongating an electric current arc to facilitate extinguishment thereof.

6. An arc plate assembly for a circuit breaker comprising a plurality of arc plates, each of said arc plates including a first and second member, said rst member being tapered along its lower portion, said second member being positioned with respect to said iirst member to form an inverted U-shaped slot between one edge of said second member and the tapered edge of said rst member, the vertex of said slot being offset from the longitudinal aXis of said arc plate, said first and second members being coplanar, resilient cord means, said resilient cord means being secured to alternate arc plates adjacent one edge and being secured to the remaining arc plates adjacent the edge opposite the said one edge to provide proper spacing for all of said arc plates.

7. An arc plate assembly for a circuit breaker cornprising a plurality of arc plates, each of said arc plates including a iirst and second member, said iirst member being tapered along its lower portion, said second member being positioned with respect to said first member to form an inverted U-shaped slot between one edge of said second member and the tapered edge of said iirst member, the vertex of said slot being offset from the longitudinal axis of said arc plate, said iirst and second members being coplanar, said cord means being secured to alternate arc plates adjacent one edge and being secured to the remaining are plates adjacent the edge opposite the said one edge to provide proper spacing for all of said arc plates, said resilient cord means having a shock absorbent characteristic to absorb the impact imparted to said arc plates caused by a circuit breaker tripping operation to prevent breakage of said arc plates.

8. An arc plate assembly for a circuit breaker comprising a plurality of arc plates, each of said arc plates including a first and second member, said first member being tapered along its lower portion, said second member being positioned with respect to said first member to form an inverted V-shaped slot, the vertex of said slot being offset from the longitudinal axis of said arc plate, the height of said second member being slightly less than the height of said tapered edge to form a gap along the edge dened by said first and second members to provide for maximum horizontal elongation of an arc for-med during a circuit breaker tripping operation, said first and second members being coplanar, resilient cord means for positioning and securing said arc plates in a spaced parallel arrangement, said cord means being secured to the opposite edges alternate arc plates to provide proper spacing for all of said arc plates.

9. An arc plate arrangement comprising a two-piece arc plate including first and second arc plate members, each of said members being formed of the same material, said first and second members being positioned coplanar to each other, said first member being tapered towards its upper edge, said second member being tapered towards its lower edge, the tapered sides of said first and second members being positioned adjacent one another to form an inverted slot between said first and second members.

10. An arc plate arrangement comprising a two-piece arc plate including first and second arc plate members, each of said members being formed of the same material, said first and second members being positioned coplanar to each other, said first member being tapered towards its upper edge, said second member being tapered towards its lower edge, the tapered sides of said first and second members being positioned adjacent one another -to form an inverted slot between said first and second members, said inverted slot being offset from the central axis of said second arc plate member.

11. An arc plate arrangement comprising a two-piece arc plate including first and second arc plate members, each of said members being formed of the same material, said irst and second members being positioned coplanar to each other, said rst member being tapered towards its upper edge, said second member being tapered towards its lower edge, the tapered sides of said first and second members being positioned adjacent one another to form an inverted slot between said first and second members, bonding means for sealing said first member to said second member, said bonding means being further adapted to space said two-piece arc plate from adjacent arc plates.

References Cited by the Examiner UNITED STATES PATENTS 2,905,792 9/59 Caswell 200-144 2,970,197 l/6l Frink 200--144 BERNARD A. GILHEANY, Primary Examiner. MAX L. LEVY, Examiner. 

1. AN ARC PLATE ASSEMBLY FOR A CIRCUIT BREAKER COMPRISING A PLURALITY OF TWO-PIECE ARC PLATES, THE MEMBERS COMPRISING EACH OF SAID TWO-PIECE ARC PLATES BEING COPLANAR, RESILIENT CORD MEANS SECURED TO SAID ARC PLATES FOR POSITIONING AND SECURING SAID ARC PLATES IN A SPACED PARALLEL ARRANGEMENT; EACH OF SAID TWO PIECE ARC PLATES BEING ADAPTED TO FORM A NOTCH THEREBETWEEN FOR GUIDING AND ELONGATING AN ELECTRIC CURRENT ARC TO FACILITATE EXTINGUISHMENT THEREOF, SAID RESILIENT CORD MEANS BEING ADAPTED TO ACT AS A SHOCK ABSORBER TO REDUCE THE IMPACT IMPARTED TO THE ARC PLATE ASSEMBLY DUE TO A CIRCUIT BREAKER TRIPPING OPERATION, SAID RESILIENT CORD BEING FORMED OF AN INORGANIC NON-CONDUCTIVE MATERIAL. 